(a) Field
The invention relates to a thin film transistor array panel and a method of manufacturing the same.
(b) Description of the Related Art
A flat panel display such as a liquid crystal display (“LCD”), an organic light emitting diode display (“OLED” display), an electrophoretic display and a plasma display includes plural pairs of field generating electrodes, and an electro-optical active layer interposed therebetween. The LCD includes a liquid crystal layer as the electro-optical active layer, and the OLED display includes an organic emission layer as the electro-optical active layer. One of the field generating electrodes in a pair is generally connected to a switching element to receive an electric signal, and the electro-optical active layer displays an image by converting the electric signal to an optical signal.
The flat panel display may include a display panel on which a thin film transistor, as a switching element, is disposed. The display panel including the thin film transistor may be referred to a thin film transistor array panel. Various layers of electrodes, semiconductors and the like are patterned on the thin film transistor array panel, and a mask is generally used in a patterning process.
The semiconductor is an important factor determining a characteristic of the thin film transistor. Amorphous silicon is frequently used as the semiconductor, but since charge mobility thereof is low, manufacturing a high performance thin film transistor may be limited. Further, where polysilicon is used as the semiconductor, a high performance thin film transistor may be more easily manuafctured because charge mobility of the polysilicon is high, but a relatively large thin film transistor array panel using the polysilicon may be difficult to manufacture because cost of the polysilicon is high and uniformity is low.
Accordingly, a thin film transistor adopting an oxide semiconductor having electron mobility that is higher than that of amorphous silicon, a high ON/OFF ratio of electrical current, a lower cost and a higher uniformity than that of polysilicon has been studied.
If a length of a channel in the thin film transistor is shortened owing to the adopted oxide semiconductor, charge mobility may be undesirably deteriorated due to an effect of a fringe field by a high drain bias. Further, in an etching process used in forming source and drain electrodes of the thin film transistor, since a surface of a back channel portion is damaged, reliability of the thin film transistor array panel employing the source and drain electrodes may be undesirably reduced. Therefore, there exists a need for an improved display panel and method of forming the same, which maintains a high charge mobility and reliability thereof.